Electrical switch contact



@ct. 31, 1939. L. ZICKRICK I I ELECTRICAL SWITCH CONTACT Filed April 8,1938 w .1 V m w/Wm o .1 i o ZA Mt H W A V M y Hi Patented Oct. 31, 1939UNITED STATES ELECTRICAL SWITCH CONTACT Lyall Zickrick, Schenectady, N.Y., assignor to General Electric Company, a corporation of New YorkApplication April 8, 1938, Serial No. 200,937

11 Claims.

The present invention relates to electrical make-and-break switchcontacts and more particularly to switch contacts which are capable ofresisting relatively heavy current inrushes without welding of thecontacts. Heretofore non-welding switch contacts have been produced.Generally, however, such contacts are expensive since they usuallycontain a large quantity of silver.

It is one of the objects of the present invention to provide a switchcontact which not only resists welding under heavy current loads andheavy current inrushes but which is also relatively in expensive.

The novel features which are characteristic of my invention are setforth with particularity in the appended claims. The invention itselfhowever will be better understood by reference to the followingspecification when considered in connection with the accompanyingdrawing in which the single figure is a perspective view of a switchembodying the features of the present invention.

I Referring more particularly to the drawing, I have indicated at l amovable switch contact member which has a rocking action against astationary cooperating contact member 2. Both contacts consist of analloy containing preferably about 9'7% copper, 2.5% lead and about 0.5%selenium. The alloy usually is made by introducing a master alloyconsisting of about 80% lead and 20% selenium and having a melting pointof about 980 to 1000 C. into molten copper. The resulting molten alloymay be cast into strips having a desired thickness and the stripsthereafter cut into sections as indicated at I and 2 on the drawing.

Switch contacts of the above composition have a resistivity of about2.23 microhms per cm Contacts about in diameter and about 3 5'" thickhave withstood, without welding, approximately 45,000 operations on aswitch test employing a 300 ampere inrush current.

Although I prefer to employ a switch contact having the compositionindicated above, my invention is not limited to the specific percentagesof ingredients recited. In general, the switch contact may have a leadcontent within the range of about 0.8% up to about the seleniumconstituting about 0.2% up to about 5% with copper the remainder. Goodresults have been obtained however with a contact which consists ofcopper and selenium, the selenium comprising about 0.2% to about 5% ofthe content of the alloy, and preferably about 3%.

I prefer to employ copper as the main ingredient of the alloy. However,if desired, a small quantity, for example up to about 10%, of anothersoft, high conducting metal, such as silver, may be substituted for apart of the copper. The presence of silver however does not improve theproperties of the contact.

.switch being characterized by its resistance to welding action uponrelatively heavy current inrush.

2. A switch contact consisting substantially of about 97% copper andabout 3% selenium.

3. A switch contact containing at least 85% of metal from the groupcopper and silver but containing an appreciable quantity of lead and atleast 0.2% selenium, said contact being characterized by its resistanceto welding upon relatively heavy current inrush.

4. A switch contact alloy characterized by its low resistivity and itsresistance to welding action upon relatively heavy current inrush saidalloy containing at least 85% of metal from the group copper and silverand 0.2% to 5% selenium, the silver when present comprising notappreciably more than 10% of the content of said alloy.

5. A switch contact containing at least about 0.8% of lead at least 0.2%of selenium, the remainder of the contact at least 85% of copper.

6. A switch contact consisting substantially of copper, lead andselenium, the copper content of said contact being at least 90% and theselenium contentvarying from an appreciable quantity up to about 5%.

' 7. A switch contact containing about 97% copper, about 2.5% lead, andabout 0.5% selenium.

8. A switch contact containing about 0.8% to about 10% lead, about 0.2%to about 5% selenium with the remainder copper.

9. A switch contact containing at least 85% copper and at least 0.2%selenium.

10. A switch comprising a stationary contact and a movable contact, eachof said contacts consisting substantially of an alloy of copper, leadand selenium the copper comprising at least 85% and the selenium atleast 0.2% of the alloy.

11. A switch comprising a stationary contact and a movable contact eachof said contacts containing at least 85% of metal from the group copperand silver but containing appreciable quantities of lead, and at least0.2% selenium,

said contacts being characterized by their resistance to welding under arelatively heavy current inrush and by their relatively low resistance.

LYALL ZICKRICK.

